1. Field of Invention
This invention relates generally to instruments for indicating direction and altitude, and more particularly to a hand-held instrument to provide a sportsman, such as a mountain climber, with readily-readable indications either of the existing direction or altitude.
2. Status of Prior Art
In certain types of sports activity, the need exists for instruments to indicate altitude and direction, so that the sportsman knows his elevation above sea level and the direction in which he is going. One popular type of sports activity involves a hang glider, which is an unpowered flying device that seeks to emulate the flight of soaring birds and takes advantage of rising convection currents and other air movements. Modern foot-launched hang gliders have flown over 160 kilometers and have reached about 6000 meters in altitude, the gliders remaining aloft for more than 15 hours.
The basic instruments that a hang-glider sportsman requires are an altimeter and a compass. Also in need of a compass and an altimeter are mountain climbers and hikers, for it is important for these sportsmen to know their existing altitude and the direction they are taking.
A conventional pressure altimeter senses the pressure of air at an elevated level and converts the sensed pressure value to an indication of height above sea level. For this purpose, use is generally made of an aneroid barometer having an evacuated capsule whose movement in response to changes in atmospheric pressure is sensed to provide an altitude reading. And the conventional direction indicator is a magnetic compass consisting of a magnetized needle mounted so as to be free to align itself with the horizontal component of the earth's magnetic field.
But sportsmen who operate a hang-glider or who climb mountains must not only have instruments that they can hand carry, but they must be able to read these instruments without difficulty under conditions of stress or under adverse environmental conditions. These instruments must not only be compact and light-weight, but it is vital that they also be reliable and accurate in operation and easily readable, even under difficult circumstances.